I. Field
The present disclosure relates generally to communication, and more specifically to transmission schemes for wireless communication.
II. Background
In a wireless communication system, a transmitter (e.g., a base station or a terminal) may utilize multiple (T) transmit antennas for data transmission to a receiver equipped with one or more (R) receive antennas. The multiple transmit antennas may be used to increase system throughput by transmitting different data from these antennas and/or to improve reliability by transmitting data redundantly. For example, the transmitter may transmit a given symbol from all T transmit antennas, and the receiver may receive multiple versions of this symbol via the R receive antennas. These multiple versions of the transmitted symbol generally improve the receiver's ability to recover the symbol.
Transmission performance may be improved by exploiting the spatial dimension obtained with the multiple transmit antennas and, if present, the multiple receive antennas. A propagation path exists between each pair of transmit and receive antennas. T-R different propagation paths are formed between the T transmit antennas and the R receive antennas. These propagation paths may experience different channel conditions (e.g., different fading, multipath, and interference effects) and may achieve different signal-to-noise-and-interference ratios (SNRs). The channel responses for the T-R propagation paths may vary from path to path and may further vary across frequency for a dispersive wireless channel and/or over time for a time-variant wireless channel.
A major drawback to using multiple transmit antennas for data transmission is that the channel response between each pair of transmit and receive antennas (or each propagation path) typically needs to be estimated in order to properly receive the data transmission. Estimation of the full channel response for all T-R transmit and receive antenna pairs may be undesirable for several reasons. First, a large amount of link resources may be consumed in order to transmit a pilot used for channel estimation, which in turn reduces the link resources available to transmit data. Second, channel estimation for all T-R transmit and receive antenna pairs increases processing overhead at the receiver.
There is therefore a need in the art for transmission schemes that can ameliorate the need to estimate the full channel response for all transmit and receive antenna pairs.